The present invention relates to a ratchet wrench and, more particularly, to a ratchet wrench that is easy to manufacture while providing reliable switching of the driving direction of the ratchet wrench.
A ratchet wrench generally includes a body having a head. In a type of reversible ratchet wrenches, the head includes a mounting recess rotatably receiving a ratchet wheel. The head further includes a receiving recess slideably receiving a pawl member. A direction control knob includes a shaft coupled with a driving member that is pivotally connected to the pawl member. Thus, pivotal movement of the direction control knob causes sliding of the pawl member and changes the coupling relationship between the pawl member and the ratchet wheel, thereby changing the driving direction of the ratchet wrench. The head further includes a positioning hole receiving a ball biased by a spring to position the direction control knob. An example of such a reversible ratchet wrench is disclosed in U.S. Pat. No. 7,146,883. However, the costs for manufacturing the body with the mounting recess, the receiving recess, and the positioning hole are high. Formation of the positioning hole coaxial with the longitudinal axis of the body is particularly difficult. Furthermore, the direction switching of the ratchet wrench including only one pawl member is not reliable.
In another type of reversible ratchet wrench, the head includes a through-hole rotatably receiving a drive member. A recess is defined in an inner periphery of the through-hole and receives two pawls each having a protrusion. A spring is mounted between the pawls to bias the pawl to engage with the drive member. The protrusions of the pawls extend into a recessed area defined in a side of the head. A control member is rotatably received in a central hole in the recessed area. The control member includes two dents in an underside thereof. The recessed area further includes a positioning hole receiving a spring and a ball biased by the spring into one of the dents corresponding to two opposite driving directions of the ratchet wrench. An example of reversible ratchet wrenches of this type is disclosed in U.S. Pat. No. 6,981,434. Such a ratchet wrench is easier to manufacture and has more reliable direction switching effect than the above-mentioned type. However, the direction switching effect is still unsatisfactory, for the protrusion of each pawl is liable to disengage from the switch.
Furthermore, fatigue of the springs or undesired distortion during movement of the switch causes a malfunction in the driving direction switching of the ratchet wrenches of both types. Further, unreliable positioning occurs when the ball wears out due to repeated rolling in the positioning hole. Unreliable positioning also occurs when movement of the ball is obstructed due to existence of impurities in the positioning hole or due to rusting of the ball and/or the spring resulting from entrance of moisture into the positioning hole.
Thus, a need exists for a ratchet wrench that is easy to manufacture while providing reliable driving direction-switching operation.